The subject of this chapter is to investigate the use of knowledge from a number of experts in developing an expert system for rating valuation of commercial and industrial properties in Malaysia. This chapter examines (1) a review of the background to the research (2) the process of eliciting the knowledge (3) the knowledge that has been elicited (4) a description of the prototype (i.e. the system that represents the knowledge) and its evaluation and (5) the conclusions drawn from the research.